The subject matter of this disclosure relates generally to wind turbine blades, and more particularly to a compact curled winglet structure for a wind turbine blade.
Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known airfoil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
To ensure that wind power remains a viable energy source, efforts have been made to increase energy outputs by modifying the size, configuration and capacity of wind turbines. One such modification has been to include a wingtip device, such as a winglet, at the tip of each wind turbine rotor blade. Generally, winglets can be employed to improve the overall efficiency and performance of a wind turbine. For example, a winglet may decrease the amount of spanwise flow generated at the tip of a rotor blade and, thereby, reduce drag on the rotor blade. Winglets may also be installed on rotor blades to reduce the overall diameter of the wind turbine as well as to reduce noise emitted by the blades. Further, winglets may also provide an increase in the power coefficient of a wind turbine and, thus, reduce the cost of energy generated by the wind turbine.
Several technologies have been employed in the past to reduce the tip vortex penalty on wind turbine blade performance with winglets being the most common passive concept. Winglets primarily rely on suppressing vortex formation to improve the lifting performance of the outboard section and mimicking an enlarged span. These winglets however have associated weight, drag/thrust and load penalties that result in the cost of energy (CoE) impact being significantly smaller than the annual energy production (AEP) gain they achieve. Further, since winglets are passive devices, they can only be tuned for one operating condition and will work sub-optimally at other conditions.
Modern wind turbine blades that employ winglets traditionally use L-shaped pressure side and/or suction side winglet structures. Suction side L-shaped winglet structures for wind turbine blades run into tower-strike margin issues that limit their size and effectiveness in enhancing aero performance. Pressure side L-shaped winglet structures for wind turbine blades are generally less effective.
In view of the foregoing, there is a need for a wind turbine blade winglet structure that overcomes the foregoing disadvantages to provide more optimal aerodynamic shapes. The improved wind turbine blade winglet structure should reduce tip vortex losses responsible for induced drag and thrust loads in the outboard section of the wind turbine blade.